Tumor-specific epitopes have been a recent focus in research involving cancer therapeutics. For example, mutated EGF-R (EGF-RvIII) expressed by breast cancer patients' tumors has been noted to be immunogenic in 50% of the patients (Purev E, et al. J Immunol 2004; 173:6472-80). Patients had both humoral and cellular immune responses specific for the mutated epitope. Induction of an idiotypic network against mutated p53 has resulted in tumor growth inhibition in mice (Ruiz P3, et al. Nat Med 1998; 4:710-2). Mutated ras protein/peptide vaccines have induced CTL in mice and cancer patients and have inhibited growth of established tumors in mice (Fenton R G, et al, J. Natl. Cancer Inst 1995; 87:1853-61; Khleif S N, et al. J Immunother 1999; 22:155-65). A peptide of EGF-RvIII has protected mice against challenge with tumor cells and this effect may have been mediated by CTL and/or antibodies (Moscatello D K, et al, Cancer Res 1997; 57:1419-24). Furthermore, anti-idiotypic antibodies mimicking the mutated epitope of EGF-RVIII have inhibited melanoma growth in mice through the induction of mutation-specific antibodies (Pinilla-Ibarz J, et al., Blood Rev 2000; 14:111-20). Circulating antibodies to mutated p21ras, bcr-ab1 and p53 have been observed in cancer patients (van Denderen 3, et al. J Exp Med 1989; 169:87-98; Takahashi M, et al. Clin Cancer Res 1995; 1:1071-7; and Scanlan M J, et al. Int J Cancer 1998; 76:652-8).
However, mutated tumor-specific epitopes recognized by cancer patients' T cells are usually individual-specific (Wang R F, Rosenberg S A. Immunol Rev 1999; 170:85-100; Baurain J F et al. J Immunol 2000; 164:6057-66; and Gambacorti-Passerini C, et al., Blood 1993; 81:1369-75), and therefore they do not provide immunotherapeutic targets for a larger population of patients.
BRAF is an intracellular signaling protein expressing frequently in melanomas for which alleles were identified as somatic mutations in 70% of melanomas, the majority of all types of nevi, and a minority of other cancers including lung, colon and ovary carcinomas, but not in normal cells (Davies H, et al. Nature 2002; 417:949-54; Brose M S et al. Cancer Res 2002; 62:6997-7000; Pollock P M et al. Nat Genet. 2003; 33:19-20.-3). The BRAF mutations were located in exons 11 or 15, with BRAFV600E representing nearly all (92%) the BRAF alleles in melanoma. BRAFV600E was previously known as V599E and was renamed by NCBI based on newly available sequence data; accession number NM—004333.2 (Michaloglou C., et al., Nature, Aug. 4, 2005, Vol. 436, pp. 720-724), replaced by accession number NM—004333.3. BRAFV600E has oncogenic activity (in vitro transformation of NIH/3T3 cells, as demonstrated in colony formation assay) through activation of the MAP kinase pathway (Davies et al, cited above).
A 29-mer BRAF peptide incorporating the V600E mutation and the sequence EDLTVKIGDFGLATEKSRWSGSHQFEQLS (SEQ ID NO: 1) was used for in vitro stimulation of lymphocytes derived from melanoma patients, generating MHC class II-restricted CD4+ T cells specific for this peptide (Sharkey M S et al, Cancer Res 2004; 64:1595-9). The patients' CD4+T lymphocyte proliferation was HLA class II (DPB1*0401 or DRB1*0404)-dependent. It is unclear from this study whether the T cells were specific for the mutated epitope of BRAFV600E.
Additionally, HLA class I (B*2705)-dependent CTL responses specific for BRAFV600E and unrelated to wild type (wt) BRAF have been described in melanoma patients (Andersen M H et al. Cancer Res 2004; 64:5456-60) in experiments using the 9-mer peptides FGLATEKSR and GRFGLATEK (SEQ ID NOs: 2 and 3, respectively). CTL were obtained by stimulation of lymphocytes with a modified BRAFV600E peptide and the CD8+T cells were enriched to demonstrate CTL activity. The HLA restriction element (B*2705) used by the patients' T cells for BRAFV600E recognition is expressed by a low fraction of individuals (3.2% Gjertson D W, et al, HLA. Los Angeles: UCLA Tissue Typing Laboratory; 1997. p. 174-427). This low population frequency (3.2%) of the HLA restriction element (B*2705) limits the potential clinical utility of these peptides as vaccines for melanoma patients,
Thus, there remains a need in the art for compounds and pharmaceutical compositions and methods useful for treatment, prevention and diagnosis of melanoma in a large majority of patients.